volumefreespace isssue on remote servers

description

I am using policies in combination with EPM framework (see codeplex) to execute policies remotely. For some reason I cannot exec the volumefreespace facet on remote servers. The powershell script which fires the policies is executed in a job and I am using
admin credentials/proxies to run this jobstep. The CMS server is 2008R2 and I got errors on both 2008 en 2012 servers (all remote). It must be a security issue, but I can't figure out what I forgot. Any ideas?